生物表面活性剂去除土壤中重金属铬的研究

发布时间：2018-05-14 14:57

  本文选题：土壤 + 重金属　； 参考：《广西大学》2015年硕士论文

【摘要】：土壤铬(Cr)污染对粮食安全、生态系统以及人类健康具有很大的潜在危害,已成为全球性的重大环境问题。土壤清洗技术是被广泛使用的一种高效修复方法,该技术的关键是有效的清洗剂。生物表面活性剂因其环境友好性成为新型的土壤清洗剂,被用于清洗土壤中的Cu、Zn、Pb、Ni、Cd等重金属,但其对Cr的应用研究较少。因此本文以单一人工铬污染土壤为供试材料,通过振荡提取实验,分别研究了两种生物表面活性剂鼠李糖脂和皂角苷去除铬的可行性,探讨了浓度、pH值、振荡时间、土水比、提取次数和提取剂组合六个因素对铬去除率的影响,分析了不同提取剂处理后土壤Cr形态和Cr(VI)的变化情况。所得结论如下：(1)鼠李糖脂和皂角苷能够有效地去除污染土壤中的重金属铬。提高生物表面活性剂浓度、增加提取次数以及延长振荡时间,均有助于提高铬去除率；碱性条件有利于鼠李糖脂对铬的去除,而皂角苷在酸性范围对铬的去除效果较好；在一定程度上,降低土水比可以提高铬去除率；在鼠李糖脂浓度为10 g.L-1,pH=10,土水比为1：20,提取时间为24 h,提取次数为5次的条件下,土壤的铬去除率可达96.08%；浓度为10 g.L-1, pH=5.5,土水比为1：20,提取时间为24 h,提取次数为5次时,皂角苷对土壤中铬的去除率为79.96%。(2)提取剂多种组合两步提取实验的结果表明：将EDTA(Ethylene Diamine Tetra acetic Acid)和鼠李糖脂的混配体系应用于对污染土壤中铬的去除是可行的,E-R (EDTA-Rhamnolipid)组合和R-E (Rhamnolipid-EDTA)组合对铬的累积去除率分别为85.70%和83.85%；柠檬酸和皂角苷组合体系的提取先后顺序会影响铬的累积去除率,C-S (Citric acid-Saponin)组合对铬的去除率合计为80.70%,S-C (Saponin-Citric acid)组合对铬的累积去除率为65.44%。(3)鼠李糖脂能够有效去除土壤中铬的酸提取态和可还原态,可以去除部分可氧化态铬,只能去除少量残渣态铬,去除率分别为94.47%、84.17%、25.82%和7.64%；皂角苷主要能够去除土壤中铬的酸提取态和可还原态,去除率分别为43.98%和51.84%,对可氧化态铬和残渣态铬的去除效果较差。鼠李糖脂和皂角苷对土壤中Cr(Ⅵ)的去除率分别为66.59%和58.02%；与处理前土壤对比,鼠李糖脂和皂角苷处理后的土壤Cr(Ⅵ)占土壤总铬的比例分别降低了9.54%和18.66%。鼠李糖脂和皂角苷均能降低Cr(Ⅵ)在土壤中的含量和比重,从而减轻Cr(Ⅵ)对环境的危害。
[Abstract]:Soil Cr (Cr) pollution has a great potential harm to food security, ecosystem and human health, and has become a major global environmental problem. Soil cleaning technology is widely used as a highly effective remediation method, the key of which is effective cleaning agent. Biosurfactants have become a new soil cleaning agent because of their environmental friendliness, and have been used to clean the heavy metals such as CuOZnZnPbPbPbPbN / NiOCD in the soil. However, the application of biosurfactants to Cr is seldom studied. Therefore, the feasibility of removal of chromium by two biosurfactants, rhamnolipid and saponins, was studied by oscillatory extraction experiment with single artificial chromium contaminated soil. The pH value, oscillating time and soil-water ratio of the two biosurfactants were discussed. The effects of extraction times and extractant combinations on Cr removal rate were studied. The changes of soil Cr morphology and CRV I after different extractant treatments were analyzed. The conclusion is as follows: rhamnolipid and saponins can effectively remove chromium from contaminated soil. Increasing the concentration of biosurfactant, increasing the extraction times and prolonging the oscillation time can improve the removal rate of chromium, while the alkaline conditions are favorable to the removal of chromium by rhamnolipid, while the removal effect of saponins is better in the acidic range. To a certain extent, reducing the ratio of soil to water can improve the removal rate of chromium, under the condition that the concentration of rhamnolipid is 10 g 路L ~ (-1) pH ~ (-1), the ratio of soil to water is 1: 20, the extraction time is 24 h, the times of extraction is 5 times. The Cr removal rate of soil can reach 96.08, when the concentration is 10 g 路L ~ (-1), pH is 5.5, the ratio of soil to water is 1: 20, the extraction time is 24 h, and the extraction times are 5 times. The results of two-step extraction experiment show that it is feasible to apply the mixture of EDTA(Ethylene Diamine Tetra acetic Acid) and rhamnolipid to the removal of chromium from contaminated soil. The cumulative removal rates of chromium in combination with R-E Rhamnolipid-EDTA were 85.70% and 83.85, respectively, and the order of extraction of citric acid and saponins would affect the cumulative removal rate of chromium. The total chromium removal rate of the combination was 80.70S-C Saponin-Citric acidin (80.70S-C Saponin-Citric acidin) and the total chromium removal rate was 80.70S-C Saponin-Citric acid.The extraction order of citric acid and saponin was 80.70S-C Saponin-Citric acidin. Rhamnolipid can effectively remove the acid and reductive forms of chromium in soil. Only a small amount of residual chromium can be removed, and the removal rates are 94.477.17% 25.82% and 7.64%, respectively. Saponin can mainly remove the acid extract and the reducible form of chromium in the soil. The removal rates were 43.98% and 51.84% respectively. The removal efficiency of oxidizable chromium and residual chromium was poor. The removal rates of Cr (鈪，

本文编号：1888364